Where are the largest and smallest Counties on the US Mainland?
and B) Is Hawaii Divided into Counties too?

Here's a partial answer to your question Bedstor....
In Hawaii:

The county is the municipal level of government, similar to some single tier municipalities in Ontario, Canada (EX: Norfolk County, Prince Edward County, Brant County); there are no incorporated cities other than the consolidated City & County of Honolulu. No formal level of government below that of the county exists in Hawaii.

Found these Bedstor, they might help
here and here(scroll down to statistics.)

Thanks Jenny
I seem to have opened a really complex area especially on your 2nd link.
All I wanted to know was the land area size yet I cannot find any references in all the numbers (unless its written deeper?)
Our (UK) local government setup is simple in relation to theirs

From Jenny's second link, it appears that Kalawao County, Hawaii is the smallest county in the country, at 13 square miles. The smallest on the mainland is New York county, at 22 square miles (from the census, Wikipedia has had the wrong number). It's actually the second smallest as well, since none of Hawaii's other counties are that small.

Also from Jenni's link, the largest US county is North Slope Borough, Alaska at 94,763 sq. mi. The largest in the contiguous states is San Bernadino, California, at 20,062 (I didn't check those against the Census Bureau).

Many thanks for that Methos

Additional question. Do they give nicknames to counties? Or a motto like they do to States ? The biggest county will be something like "Welcome to the Big Country County"

Some U. S. Counties have mottos. More often than not, newer mottos are a product of economic development efforts to attract new businesses or tourism. Some of the "new" mottos in counties near me are:

"A connected community ... with the stability of the past and the promise of the future."

"More than you can imagine."

"Where the past is still present."